Perfect Temperature for Nursery?

What is the recommended temp. to keep my son's nursery at? We live upstairs and don't always have full control of the temp in the house (my dad is picky) but my son will also be upstairs and I'm afraid it'll get too hot for him. How cool/warm should we keep the upstairs for him? It's usually about 78-80 degrees upstairs and it feels like I'm suffocating as it is. What should we try to keep the temp at? Also, I'm due July 4th so it'll be getting really hot outside when he's born.